The participants of the expedition (BirdLife International, Aquatic Warbler Conservation Team)arrived safely and healthy at home. The planned schedule of the expedition could be successfully performed.
The outstanding importance of the Djoudj area for wintering AW was confirmed.
For instance, the team caught two AW that were ringed there one year before at the same place (site fidelity).
Nevertheless, the situation of suitable grass marshes in the western Sahel is alarming! Obviously there have been tremendous losses of this habitat type during the past 2-3 decades.
– Recent AW wintering sites were not found.
– The habitats in the Diawling NP are partly potentially suitable, but were almost (>95 %) dry in mid-January 2008. There are large areas, which might have been suitable for AW in November and December (and probably still during the moulting period), but in mid-January were dried out. Intensive mist-netting at remaining wet patches brought many sedge warblers, but no AW record. There might be still a few AW, but density must be low.
– A large area N of the Senegal River N of the Djoudj NP, which looked very suitable in older satellite images, has been transformed into a fresh water reservoir and is now overgrown with the invasive cattail Typha australis – and thus lost as AW site.
– Other potential sites near and NE of Rosso were not accessible or not suitable (dry or too small).
– The area N Nouakchott was not visited, because it is an unsuitable habitat type (periodical salt lake without vegetation).
– Some other potential sites in South- or Southeast-Mauritania suggested by Bruno Lamarche should be visited in future, but are very hard to access.
– There are no more large suitable habitats along the Senegal river up to the border of Mali. Within the recent floodplain, there are only very few small patches of suitable habitat (Cyperis marshes) at some lakes. Intensive mist-netting at the two best sites brought no AW records. If there are wintering AW at all, the total number must be very small.
– A large suitable habitat area was discovered in the Ndiael Wildlife Reserve S of Ross-Bethio, south of Djoudj (also in the Senegal delta). This area might have been suitable until late December/early January (moulting period), but was almost dry in late January. Intensive mist-netting at the remaining wet parts brought also no AW capture; thus, the number there must be also small.
– The Djoudj area (inside and outside the NP) remains the only large suitable AW wintering site in West-Africa known so far. But also here, habitat conditions were not optimal in this winter, because less water was let into the inundation zones due to management purposes: The big White Pelican colony on an island is threatened by soil erosion and has to be stabilised with big machines in April/May. To get the area dry for these measures, water supply of the whole Djoudj area was reduced. This reduced also the area of suitable AW habitats during the late winter (February) in a substantial degree.
The situation will hopefully improve after the next raining season.
– Systematic research has now started in the Djoudj area (doctor thesis of Cosima Tegetmeyer). 14 AW have been captured during the short stay and 4 have been fitted with radio transmitters (1 is still active). The results should help to give proper management advice to the NP administration.
For more information contact: Dr. Martin Flade, AWCT